The present invention relates generally to automotive service equipment incorporating vehicle wheel turn plates and slip plates, such as vehicle support systems and vehicle lift racks, and in particular, to a deflection resistant combination of a vehicle wheel turn plate and slip plate establishing a precision planar surface for receiving a vehicle steered wheel.
Typically, movable surfaces commonly referred to as turn plates and slip plates are placed on a vehicle support system surface onto which a vehicle undergoing an alignment measurement or adjustment procedure is disposed, such as a lift runway, as shown in FIGS. 1A and 1B. A turn plate is typically a round plate mounted on a bearing surface, flush with the surface of the vehicle support system. The turn plate permits the steered wheels of a stationary vehicle to be steered from side to side without requiring lifting of the vehicle, and simultaneously permits limited motion in a horizontal plane. A slip plate is similar in configuration, but is generally rectangular, and permits only motion in the horizontal plane, without permitting any rotational movement. These movable surfaces are commonly utilized in order to prevent the vehicle suspension from binding during movement of a vehicle required by an alignment adjustment or measurement process. Prior to driving a vehicle over the vehicle support surface, and at certain times before and during the measurement of a vehicle suspension system, these movable surfaces must be locked into position to prevent unintentional movement of the vehicle.
For example, during a conventional vehicle wheel alignment procedure, the vehicle is driven onto the vehicle support system with the movable surfaces in a locked configuration. Next, sensors are mounted to the vehicle wheels, and the sensors compensated before actual vehicle alignment measurements are acquired. The compensation procedure is required to eliminate errors in alignment angle measurements resulting from runout of the vehicle wheel, the wheel adaptor, or wheel alignment sensor mounting shaft, if present. The compensation procedure can be performed by rotating the vehicle wheels with the vehicle raised off the runway surface, or alternatively, by rolling the vehicle over a limited range on the runway surface with the wheel alignment sensors attached to the wheels, i.e. “rolling compensation”
To carry out the procedure for rolling compensation, it is required that the vehicle be rolled a short distance onto the turn plates, such as shown in U.S. Pat. No. 6,209,209 B1 to Linson et al., which is herein incorporated by reference. To carry out a short-distance variation of the procedure for rolling compensation, it is required that the vehicle be initially disposed with the front steered wheels approximately centered on the turn plates. The vehicle is then rolled forward a short distance, about 10-15 degrees, to the front edge of the turn plate, rolled back about 20-30 degrees, to the rear edge of the turn plate, and then rolled forward again to approximately the starting position on the turn plate. Measurements are acquired at multiple rotational positions of the vehicle wheels during this sequence.
Often, temporary devices are used to “bridge” the gaps which are present between the runway surfaces and the edges of each turn plate, permitting the vehicle to roll easier and have some support if the roll procedures carry the vehicle off either the front or rear edges of the turn plate. Following the compensation procedure, the bridges, if present, are removed to avoid interfering with the range of motion of the turn plate. The alignment measurements and any corrective procedures are then carried out in a conventional manner during which the movable surfaces may be locked into a stationary configuration from time to time as required, such as shown in U.S. Pat. No. 7,308,971 to Liebetreu et al., which is herein incorporated by reference.
During the rolling compensation procedures, measurements are acquired which are sensitive to movement of the vehicle suspension. In particular, it has been found that the rolling of the vehicle wheel assembly over the gap between the runway surface and the edge of the turn plate and/or slip plates can induce undesired reactions in the vehicle suspension system, and correspondingly, reduce the accuracy of measurements acquired during the rolling compensation procedures. Similar effects have been noted due to physical deflection of the turn plate surface away from a horizontal alignment due to an uneven distribution of weight from the vehicle as the vehicle wheel assemblies roll towards the respective forward and rear edges.
Accordingly, it would be advantageous to provide a vehicle support structure such as a floor, runway, or lift-rack surface with one or more turn plate/slip plate elements in a configuration which maintains a precision planar surface to within a measurement tolerance as a vehicle is driven across, and which reduces undesired reaction in the vehicle suspension system induced due to the presence of voids, gaps, or spaces in the vehicle's travel path.